This invention relates to the field of optical resonators.
In order to form a passive high-Q optical resonator, one or more of the mirrors forming the optical cavity is usually curved to compensate for optical diffraction within the cavity. This requirement complicates the fabrication of such resonators since curved mirrors usually require individual handling. In addition, once such a curved-mirror optical resonator is constructed, the cavity mode is precisely defined, and optical input to the cavity must be precisely aligned to couple efficiently to that mode.
An alternative approach is to use two-mirror, plano-plano, optical cavities. Such cavities can easily be produced by polishing two sides of a crystal (or other material) flat and parallel. The two polished sides can then be dielectrically coated to form mirrors. The resulting cavity has translational symmetry in the plane perpendicular to the cavity axis. This makes alignment of the optical input to the cavity easier than in the case of a curved-mirror optical resonator, and allows the positioning of the input to avoid defects in the mirrors or the material between the mirrors. Such a cavity, however, suffers from diffraction losses. In addition, the degree of parallelism required between the two polished surfaces can make the fabrication of a high-Q, plano-plano, optical resonator impractical.
The present invention provides a method of producing high-Q, plano-plano, optical resonators with greatly reduced diffraction losses and greatly reduced requirements on the parallelism of the mirrors.